During use, friction materials, such as brake linings or clutch facings, come in contact with metals, e.g., cast iron. Corrosion of such ferrous metals may cause adhesion (stiction) of the friction material to the metal when they are allowed to contact one another for a period of time. Generally, such corrosion and stiction occur before the metal and friction material have received substantial sustained wear. One longstanding approach to preventing clutch facing stiction comprises coating the friction material with sodium nitrite. However, recent and anticipated agency recommendations have created a need to replace sodium nitrate which is ecologically less than desirable. It also does not appear to retain its corrosion resistant properties longer than a few weeks (often before the friction material is operating on the vehicle), oxidizing at ambient temperatures to the nitrate. However, we have found that coatings comprising alkanolamine-carboxylic acid salts on friction materials are significantly more effective in preventing such corrosion bonding and that they maintain these properties after application and during friction material use for a substantially greater period of time.
Alkanolamine-carboxylic acid salts have been used as flame retardants in acrylic fibers, however more usually as corrosion inhibitors in lubricants, cutting fluids, radiator coolants, and metal surface cleaning-treating compositions. U.S. Pat. 3,769,214 to Davis teaches aqueous compositions, adapted for use as coolants and lubricants in metal machining operations, comprising alkanolamine salts of carboxylic acids.